In the prior art, there is disclosed a technology described in Patent Literature 1, for example as a technology of detecting steering position information from a motor rotation angle. In this technology, the steering position information is calculated on the basis of an angular signal detected during an off-state by supplying power to a dedicated magnetic detection element even when an ignition switch is in the OFF state. In such a technology, a low power consumption mode is provided, in which supply of power to the dedicated magnetic detection element stops for a certain period of time when power is supplied in the OFF state.